The present invention concerns a device for filtering dust from gas, especially a hot gas, by using tubes.
Devices of this genus are known for example from German OS 3 408 627, German Patent 3 515 365, and European Application Exposure 0 428 862. The ceramic tubes hang down in these devices. They rest by way of a flat or convex interface on an accommodation on a perforated base. The advantage of the convex joint is that it allows the tube to slant slightly in operation without detriment to the seal between the dirty-gas zone and the clean-gas zone. The ceramic tubes in the device known from the European exposure, rest on metal accommodations welded to a dirty-gas channel. The mutually contacting surfaces of both the tube and the accommodation are concave and convex. Since the ceramic that the tube is made of and the metal that the accommodation is made of have different coefficients of heat expansion, however, the contact surfaces can become distorted. This situation makes it impossible to ensure absolute tightness at high temperatures, and the requisite level of dust elimination cannot always be attained. The same difference in heat-expansion coefficients may generate enough stress in the contact surfaces to crack the tube.
Inserting mineral seals between the ceramic tube and the metal accommodation in order to compensate for the difference is known from the aforesaid exposure and from U.S. Pat. No. 4,735,638. Since such seals are made of loosely compacted fibers, however, they cannot unless specially adapted withstand the conditions that accompanies the operation of such a gas filter. These conditions are characterized by rapid alterations between the pressure inside the tube and that of the atmosphere around it. The special adaptations comprise springs or stuffing-boxes between the tube and the accommodation. Such structures make the device more expensive, and complicate installing and removing the tubes.
Also known (from German OS 4 126 320 and OS 4 126 324) are adapters that fit into the accommodation and are sealed off with resilient seals. Resilient seals of organic materials, however, do not resist heat very well and will burn or pyrolyze, depending on how hot the gas is and how much oxygen it contains.